1. Field of the Invention
The present invention generally relates to electrolytic systems that employ ion exchange membranes and fluids corrosive to such membranes and/or system hardware, and more specifically, to a method for preventing degradation of the membrane and/or hardware during system shutdown.
2. Description of Prior Art
Semiconductor production, biotechnology, and other applications require the use of ultrapure water. Such high-purity, pure water is achieved by water purification systems that subject feed water to treatments or techniques that target ionic and nonionic substances, in addition to, microorganisms, such as bacteria. Recent advances in ion exchange resin treatments or distillation techniques enable the near elimination of free ions in such high purity water. Remaining dead cells of microorganisms and nonionic substances are now treated with ozone, a powerful and clean oxidizing agent. The use of ozone for water treatment is particularly advantageous where no residual substances are left in the treated water, unlike chlorine-containing oxidizing agents. The lack of residual substances is due to the fact that the product of ozone decomposition is oxygen and water and to the fact that ozone is so unstable that it does not remain in treated water.
Where ozone is naturally unstable, it is necessary to generate it on site. The production of ozone on the industrial scale has taken place by means of corona-type electrical discharges in air or oxygen. However, existing corona discharge technology is often too expensive to implement or too difficult to maintain at various sites. As a result, alternate technologies, that allow for cost effective, on-site generation of ozone, have been sought.
Electrolytic systems or devices for ozone generation, which resemble standard solid polymer electrolyte electrolysis units, have proven to be one such viable alternative to conventional corona discharge systems. Such electrolytic systems have the advantage of being able to obtain a high concentration of high-purity ozone gas through use of one or more small-sized electrolytic cells. Unfortunately, a life problem associated with the presence of ozone in the system during system shutdown has been identified. In particular, physical deterioration of the ion exchange membrane employed, greatly increased (if not disabling) cell voltage requirements on system restart and resultant shortened or limited cell life has been observed.
It is, therefore, a principal object of the present invention to provide a method for preventing degradation or deterioration of ion exchange membranes and/or system hardware employed in electrolytic systems.
It is yet a further object of the present invention to provide a method for stabilizing cell voltage requirements on system restart and for prolonging cell life.